HARVEST TECHNOLOGY
216
62 LANDTECHNIK 4/2007Peter Wacker and Stefan Böttinger, Hohenheim
Combine Harvesters – State of the Art
E
ven though the development has already reached a high level, the combine ma- nufacturers continued to raise output and operating comfort last year. The new or im- proved products which will be presented at the Agritechnica 2007 are interesting. Three manufacturers (Claas, CNH, and John Deere) supply more than 90 % of the German market, and five other brands (Deutz-Fahr, MF, Fendt, Laverda, and Sampo) share the rest. In Germany, approximately 90 combine models ranging from 75 kW to 398 kW are offered (Fig. 1). In the past 50 years, the lowest engine output increased approximate- ly three-fold to 75 kW. In the upper power segment, engine output grew almost 10-fold to 398 kW. Engine power is going to keep in- creasing in the future so that throughputs can grow even further. More and more engines meet the exhaust standard Tier III and reduce fuel consumption as well as noise both at the driver´s place (better cab design) and in the environment. Oil consumption was reduced, and oil change intervals were extended. In 2006, a total of 2206 units were sold in Ger- many, i.e. only 22 combines less than in the previous year.Combining Costs
The production costs of grain vary signifi- cantly not only worldwide, but also within Europe. Different cost structures for produc- tion in Germany, France, the Czech Repub- lic, and Canada were shown using several farms as examples. In Canada, in particular the expenses for labour and machinery a-
mount to only one third of the costs in France and Germany, which is a result of the different intensity of cultivation.
In certain cultivation techniques, the com- bine could be used for direct drilling, which would allow one pass and, hence, costs to be saved.
The stabilization of the grain prices is being supported by the growing market for energy grain (bio-ethanol, biogas, combus- tion) and for industrial use (starch).
More and more often, the growing size of combines is confronting the buyer with the question of whether he should buy one larger machine instead of two. Due to the lower personnel expenses, the use of a more effi- cient combine provides considerable advan- tages. In practice, repair costs vary greatly and mainly depend on local and individual circumstances.
Performance-based cost calculation, which is discussed frequently, is used only rarely in practice because evaluation is more difficult than in area-dependent cost calcula- tion. Haulage is a very important cost factor and contains additional optimization poten- tial. During transports over large distances, for example, it is worthwhile to use trucks more frequently. On large farms, more and more grain carts are used on the field.
Larger operations are also increasingly con- sidering grain storage instead of direct sale again. This requires large combine output so that the grain can be stored dry and in high- quality condition. In addition, the grain must be cleaned, and storage space must be pro- vided.
Securing the world food supply with a rapidly growing world popu- lation necessitates further efforts to produce, harvest, process and dis- tribute increasing quantities of food, in spite of limited agricultural areas. Due to limited time, a fast, low-loss harvest is especially im- portant. Also in developing coun- tries, increasing harvest mecha- nization is necessary in order to in- crease capacity levels and reduce losses. For this reason, combines are being improved and optimized by the manufacturers. Progress in separating- and threshing techno- logy, cutter bars, drives, and chas- sis, as well as in operation and au- tomation is reported on below.
Dr. agr. Peter Wacker is a scientist working in the section Basics of Agricultural Engineering (director:
Prof. Dr.-Ing. S. Böttinger) of the Institute of Agricul- tural Engineering of Hohenheim University, Garben- str. 9, D-70599 Stuttgart.
Keywords
Combines, market development, technical optimisa- tion
Fig. 1: Increase of combine engine power
The advantages of intermediate storage on the farm are reduced waiting times for un- loading, which leads to a reduction of the re- quired transport capacity, and the sale of larger lots at the most favourable time.
Threshing and Separating Systems The threshing and separating systems availa- ble today are being improved in detail. Prin- cipally new systems have not been intro- duced on the market for a long time. Several companies, however, are developing new threshing systems with separating rotors for large combines. The high-cut technique for the reduction of the straw load on the com- bine is being discussed more intensively again. However, the user must find out whether the high stubble can be incorporated or whether an additional pass is necessary at a later time. A newly presented retrofit un- derfloor chopper for the combine opens up new possibilities here. Nevertheless, suffi- cient threshing capacity must be available for unfavourable harvesting conditions, such as laid grain. Investigations have shown that the advantages of the high cut are mainly given under moist conditions and decrease when it is dry.
Kernel damage is often underestimated as a cause of losses because some damaged ker- nels are overblown by the cleaning system in addition to the visible kernel damage in the grain tank. These fine, damaged kernels usually cannot be detected on the field, but they can account for as much as 3% of the entire grain.
Consumers are showing an increasing de- mand for alternative grain varieties. This re- quires other settings and setting possibilities of the combine. Normally, combines are suitable for special crops, such as dinkel. In these crops, however, they need to be driven more slowly.
Cutter Bars
The adaptation of the cutter bars to different harvesting conditions is simplified by the manufacturer (control of the rotational speed of the reel, automatic reel lowering). Almost
all manufacturers meanwhile offer cutter bars which allow the distance between the cutter bar and the gathering auger to be ad- justed from the driver´s seat either steplessly or in steps.
After 1960, Lely introduced foldable cut- ter bars into the market. The centrally divid- ed cutter bar had a working width of 4.2 m.
Since the two parts were able to be folded up by 90° each, a transport width of 2.9 m was able to be reached. Foldable cutter bars re- duce set-up times significantly. This advan- tage particularly manifests itself in smaller- structured regions with a large percentage of cooperatively used machines. Under these conditions of use, these cutter bars have a constant market share. The current range of cutter bars offered with their various folding concepts is shown in Figure 2. Only one combine manufacturer offers a self-pro- duced foldable cutter bar with a working width of 4.5 and 5.4 m, which reaches a transport width of 2.98 m because both halves are swivelled in the direction of trav- el. The other manufacturers offer their cutter bars for all combine brands. In these solu- tions, the parts of the cutter bar are swivelled or pushed one above the other. Therefore, transport width depends on the individual cutter bar width. Only in the best case does it reach 3.0 m.
Drives and Chassis
Hydrostatic travel drives and hydrostatic drives for different elements of combines and other harvesting machines are widely used. Alternative electric drives are being discussed and must compete with existing solutions.
With regard to their dimensions, combine chassis are reaching the limits of the Motor Vehicle Safety Regulations. For this reason, one must make sure that machines wider than 3 m are exempt from Section 70 of the Motor Safety Vehicle Regulations and apply for the permission of the local authorities for the operation of the machines according to Section 29 (3) of the Motor Vehicle Safety Regulations. With regard to soil pressure, sufficiently dimensioned tyres are required.
As a result, however, the machine widths al- lowed even with an exemption permit for transport on public roads are easily exceed- ed. For this reason, the use of tracks is re- commended. At a machine width of less than 3.5 m, they provide slightly lower soil pres- sure values than low-pressure tyres, which are considerably larger. However, costs are higher.
Operation and Automation
Future legal requirements with regard to per- missible vibrations at the work place are fa- vouring the use of cab suspensions, which are being examined by the manufacturers and will improve comfort in the future. To a growing extent, the driver is freed from rou- tine tasks and has more time for control- and optimization work. Examples are automatic steering systems as well as the control of the driving speed depending on throughput and grain losses.
Precision Farming
Yield maps have been improved using different statistical methods. It is already possible to include the dynamics of the ma- terial flow in the combine in the data recor- ded on the machine. The quantity of tai- lings and its influence on the material flow are taken into account with the aid of ano- ther baffle plate throughput sensor for tai- lings.
More and more sensors for quality measu- rement on the combine are being developed.
Experimental systems on the combine mean- while determine the protein and gluten con- tent as well as the falling number during work. The increasing contamination of grain with fusarium poisons (DON) also requires early detection and selective harvesting de- pending on the extent.
Beyond precision farming, the combine is an important link in the production chain which provides information as well as proof of quality and supports traceability. One pos- sibility is data storage during the harvest on RFID and the adding of the chips to the grain.
62 LANDTECHNIK 4/2007
217
Fig. 2: Foldable cutter bars
